A separation method using a membrane has lots of advantages over the method based on heating or phase-changing. One of the advantages is high reliability of water treatment since the water purity required can be easily and stably satisfied by adjusting the size of the pores of a membrane. Furthermore, since the separation method using a membrane does not require a heating process, the membrane can be used with microorganism which is useful for a separation process but may be adversely affected by heat.
One of the separation methods using a membrane is a separation method using a hollow fiber membrane module provided with a bundle of hollow fiber membranes. Conventionally, although the hollow fiber membrane module has been widely used in the field of precision filtration such as manufacture of axenic water, drinking water, and ultrapure water, its application range has been recently extended to sewage/waste water treatment, sludge separation from a septic tank, removal of suspended solid (SS) from industrial waste water, filtration of stream water, filtration of industrial water, filtration of pool water, and the like.
One kind of the hollow fiber membrane modules is a suction type hollow fiber membrane module which is submerged into a water tank filled with a fluid to be treated. A negative pressure is applied to the inside of the hollow fiber membranes, whereby only a fluid passes through the wall of each membrane and solid elements such as impurities and sludge are rejected. This suction type hollow fiber membrane module is advantageous in that the manufacturing cost is relatively low and that the installation and maintenance cost is reduced since a facility for circulating a fluid is not required.
In case of such a suction type hollow fiber membrane module, several hollow fiber membrane modules are inserted into a frame structure in due order to form a cassette type. Afterwards, this cassette is submerged into a liquid substrate having contaminant materials including solid elements, whereby a filtering treatment is carried out. At this time, as a water treatment is carried out, membrane contamination is caused by the contaminant materials. As a result, a problem occurs in that permeable performance of the membrane is remarkably deteriorated. Accordingly, in order to maintain permeable performance of the membrane at a good state while a water treatment is being carried out by the hollow fiber membrane, rising air bubbles are generated through the air jetted from an aeration pipe positioned under the hollow fiber membrane modules, whereby impurities are removed from a surface of the hollow fiber membrane.
Meanwhile, since the air is strongly jetted from the aeration pipe when the aeration process is carried out, the hollow fiber membrane modules are subjected to serious vibration. The hollow fiber membrane modules may be damaged by such vibration. Accordingly, a plurality of hollow fiber membrane modules constituting one cassette are tightly adhered to one another. However, if the plurality of hollow fiber membrane modules are tightly adhered to one another, damage of the hollow fiber membrane modules due to collision among them may be reduced but vibration of a bundle of hollow fiber membranes ported in each hollow fiber membrane module may still occur. Also, the hollow fiber membranes may still be damaged due to their vibration. If it is required that a specific hollow fiber membrane module should be exchanged with a new one or should be repaired due to its damage, after the corresponding one of the plurality of hollow fiber membrane modules tightly adhered to one another is ejected, it is repaired or exchanged with a new one, whereby the repaired one or new one is inserted into the corresponding position.
As described above, when a plurality of hollow fiber membrane modules are inserted into a filtration apparatus in due order to form a cassette, when a specific one of the plurality of hollow fiber membrane modules is ejected from a frame structure to repair it, and when the repaired one is again inserted into the filtration apparatus, the filtration apparatus according to the related art has much difficulty because no guide module providing insertion/ejection paths of the hollow fiber membrane exists.
The current trend is towards a large scaled hollow fiber membrane module to increase capacity of a water treatment. In this respect, a problem occurs in that difficulty in inserting/ejecting the hollow fiber membrane module into/from the frame structure becomes more serious. Particularly, in case of a horizontal hollow fiber membrane module in which a length direction of the hollow fiber membrane is parallel with an insertion and ejection direction of the hollow fiber membrane module, the above problem becomes more serious.